The present invention relates to the art of interactive image-guided surgery. It finds particular application in conjunction with minimally invasive stereotactic surgery performed in CT imaging systems using a frameless mechanical arm device to guide surgical tools such as biopsy probes or the like and will be described with particular reference thereto. It is to be appreciated, however, that the invention is also applicable to a wide range of imaging equipment and minimally invasive stereotactic surgery procedures including, for example, ultrasonic and magnetic resonance imaging devices and surgery performed using those devices.
Heretofore, several systems have been proposed combining mechanical arm type mechanisms together with human anatomy imaging devices for performing certain interventional surgical procedures such as, for example, the placement of catheters, drainage tubes, biopsy probes, or the like, within a patient's body. U.S. Pat. No. 5,142,930 teaches a mechanical arm device associated with imaging system generating one or more images of a patient's anatomy and displaying those images on a screen. A computer is used to track the location of a surgical tool connected to the mechanical arm as the arm is moved through physical space. The computer performs a transforming rotation of the physical space to the image space in order to cause the display device to show the location of the surgical tool within the patient's image space. Position feedback devices are arranged at each joint of the mechanical arm to detect rotation and angular movement of the arm segments for tracking the end tip of a tool on the arm relative to the position of fiducial implants disposed on or in the patient's body.
One disadvantage of the above system, however, is the need for a bulky stereotactic localization frame. Although the system proposed above tracks the position of the tool carried on the arm relative to the arm's base member, the use of fiducial implants remains necessary to initialize a mapping transformation between the internal coordinate system of the surgical image and the external coordinate system of the mechanical arm.
A frameless stereotactic tomographic scanner for image-guided interventional procedures that does not rely upon the bulky localization frame or the fiducial implants placed in the patient would reduce the setup time spent before surgery and, in addition, would provide a more accurate and repeatable positioning of the surgical tools or probes into the patient's body.
U.S. Pat. No. 5,622,170 teaches a surgical apparatus for determining the position and orientation of an invasive portion of a surgical probe within a patient's body. A computer associated with that system determines the position and orientation of the invasive portion of the surgical tool by correlating the position of the tool relative to a predetermined coordinate system with a position of a model of the patient's body defined in relation to the predetermined coordinate system. The modeling is accomplished by placing at least three non-collinear reference points on the patient. The reference points may be ink spots, tattoos, radiopaque beads, or fiducial implants on the patient. After the patient is imaged with the fiducial markers in place, the interventionist must place the tip of the surgical probe at each of the reference points on the patient to establish the relationship between the reference points in the model space and their current physical locations in the predetermined coordinate system of the patient space.
It would be desirable to perform image-guided minimally invasive stereotactic surgical procedures without the need for implanting fiducial markers in the patient. In addition, it would be desirable to provide an automatic transformation between a surgical tool in a localizer space and the couch upon which a patient rests in scanner space so that the position of the surgical tool, together with an image of the patient in an image space, can be displayed as a composite view on a display monitor or the like.